Various types of stabilizers are used with archery bows (hereinafter referred to as simply "bows") and other devices (such as air guns) that produce mechanical impulses. The stabilizers are intended to reduce the detrimental effects of an impulse. Generally, stabilizers comprise one or more masses that are capable of moving in approximately the same direction as the impulse and usually the motion of such masses is not only opposed by the inertia of each mass (force proportional to acceleration) but also by one or more spring means (force proportional to displacement) or by viscous damping (force proportional to velocity). The outside shape of stabilizers tends to be extended and frequently cylindrical. A threaded distal end of a stabilizer is screwed to the outside edge of a bow riser (side facing away from the archer) pointing in approximately the same direction as that in which an arrow would be propelled.
The extended shape of a stabilizer and its attachment to the front of a bow results in an awkward arrangement when in the field (where a forward protruding stabilizer is prone to get snagged) and results in a need to store the stabilizer unattached to the bow when the bow is cased (for otherwise a bow with attached stabilizer would not fit). Both of these difficulties are attenuated, or even eliminated, when an elbow is placed between a stabilizer and a bow riser.
An elbow allows a stabilizer to pivot away from its normal position (thereby producing an arrangement that is significantly less likely to get snagged while in the field and a more compact arrangement when retaining the bow in a case) and yet allows a stabilizer selectively to be locked into its normal position. One end of the elbow is attached to the bow riser (in lieu of a stabilizer) and the other end of the elbow is attached to a stabilizer. Between the two ends of the elbow are means for pivoting and means for locking the pivot.
The use of an elbow for linking a bow and a stabilizer is discussed. However, an elbow may be used with any reasonable accessory.
Known elbows are: a tube loosely receiving a bolt such that the head of the bolt is flush with one end of the tube (head end) and such that the bolt extends past the other end of the tube (bow attachment end); a cap pivotly connected to the tube where the pivot is formed by two, short pins passing through the cap and a short distance into the tube near the head end of the tube (a pin is placed on each side of the cap); and an extended adapter that has a threaded recess at one end (stabilizer attachment end) and a threaded outside on the other end (locking end). The cap contains a threaded hole for receiving the locking end of the adapter. In use, a stabilizer is screwed into the stabilizer attachment end of the adapter, the adapter is screwed into the cap, and the bow attachment end of the bolt is screwed into the bow while the tube is held so that the cap is pointing in the desired direction. Then, when it is desired to lock the stabilizer in its extended position, the cap, adapter, and stabilizer are rotated into place and the adapter is screwed down through the cap onto the head end of the tube. Six parts are involved (bolt, tube, cap, two pins, and adapter). The known variation is the addition of a seventh part in the form of a plastic washer at the very end of the locking end of the adapter. The washer is probably added to reduce the sound of the locking action.
The primary difficulty with the known elbows (above described) is their tendency to fail in the vicinity of one of the pins. Of necessity, the pins extend only a very short way into the tube (or they would interfere with the bolt) and the pins are loose in the tube (or pivoting could not be effected). Thus the force of the locking is concentrated, tending to buckle the pins and to pull the pins out of the tube.
A secondary difficulty with the known elbows is a tendency for the device to unlock or loosen after being vibrated for a while. During locking an external torque is applied to the adapter that (when the adapter reaches the end of its travel against the head end of the tube) produces a longitudinal stress that (in turn) produces a slight longitudinal strain. After the torque is no longer applied, the slight longitudinal strain sets up a force against the threads, the friction of which hold the assembly together. The overturning moment of the extended stabilizer cycles as the assembly is vibrated causing variations in the longitudinal stress that eventually tends to cause the threads to "back out." Increasing torque during locking would attenuate this undesired tendency, but would tend to cause premature pin failure because of the resulting greater stress. The addition of the prior noted plastic washer might result in slightly more residual strain for the same residual strain with negligible to minor improvement in this difficulty.
A tertiary difficulty with the known elbows stems from the use of six or seven parts. When handling the device in the field the loose bolt and adapter are prone to being lost, though the washer could be used to keep the adapter from being able to be removed. Additionally, the use of so many parts increases the cost of producing and assembling the device, particularly when there are four threaded surfaces.
Accordingly, an object of the present invention is an improved elbow that is not prone to premature pivot failure.
Additional objects of the present invention are an improved elbow with reduced tendency to unlock or loosen with vibration, fewer loose or detachable parts, fewer parts, and simplified production and assembly.